i. Field of the Invention:
This invention relates to a friction coupling device for a vehicular automatic transmission and a support mechanism for the friction coupling device.
ii. Description of the Prior Art:
The conventional support mechanism for a friction coupling device of an automatic transmission is usually constituted by a snap ring or a combination of a snap ring and a flange plate which are mounted on a stationary member such as the transmission case or on a rotational member, thereby to receive the operational load at the time of engagement of the friction coupling device.
In an automatic transmission in which a plural number of friction coupling devices are mounted in adjacent positions, however, the conventional support mechanism which consists of a snap ring or of a snap ring and a flange plate has a problem that the axial dimensions of the transmission are increased due to existence of a gap space between a hydraulic servo drum of one friction coupling device and a snap ring or a snap ring and a flange plate of an adjacent friction coupling device.
In addition, the conventional friction coupling device for automatic transmission employs a plural number of friction elements which are fitted in splines formed on a stationary or rotary member, in combination with a hydraulic servo drum which is formed integrally with the stationary or rotary member and which consists of an annular hydraulic servo drum having an outer cylinder, an inner cylinder and a side wall connecting the outer and inner cylinders, a piston fitted between the outer and inner cylinders, and return springs located outward of said outer cylinder or on a wall portion of the piston, engaging and releasing the friction coupling device by controlling flows of line pressure to and from a space between the drum and piston.
In a case where a number of friction coupling devices are mounted on a stationary member, in a row in the longitudinal direction and on one and the same circle, it is economical to form the splines on the part of the stationary member integrally according to the numbers of friction elements of the respective friction coupling devices. However, this is impossible since the hydraulic drums are formed integrally with the stationary member. Besides, when a friction coupling device is located at a distance from its hydraulic servo, the piston is required to have a long abutting surface for engagement with the friction elements along with a long side wall, lacking stability in rigidity and assemblage.